The present invention relates generally to adjustable beds, and more particularly to a single motor drive unit for an adjustable bed. The drive unit includes a toothed gear clutch assembly.
Adjustable beds are well known in the art and are used extensively in hospitals, nursing homes, and private homes by people who must spend extensive periods of time in bed for reasons of health, injury, or physical handicap. More recently, adjustable beds have gained in popularity for general home use by people who simply want to be more comfortable when sleeping, reading, watching television, etc.
In general, adjustable beds are categorized as either manual or powered. Manual beds utilize hand cranks to move the adjustable sections of the bed to the desired attitude and height, whereas powered beds use electric motors or hydraulic actuators to perform the same result.
Typically, both manual and powered beds have three, four, or even five articulated sections which may be separately adjusted. A common arrangement, for example, includes a head adjustment, a leg adjustment, and a bed height adjustment (which raises or lowers the entire bed). Usually, each adjustable section of the bed has a separate actuator, including a rotatable shaft, which turns in one direction to raise the section and in the opposite direction to lower the section.
There are advantages and disadvantages associated with both manual beds and powered beds. Manual beds are less expensive than powered beds and are usually simpler in construction, which makes them easier to repair. The disadvantages of a manual bed are the requirement that another person must be available to operate the bed (assuming the person in bed is bedridden), as well as the extra effort and awkwardness of turning the handcranks, etc. Powered beds are, of course, much easier to use and may even be controlled by the bedridden person himself. Motor-powered beds are substantially more expensive than manual beds, however, and are generally more difficult to repair as well.
Due to the high cost of powered beds, many people who require an adjustable bed in their home purchase or rent a manual bed. If, at a later time, the user wishes to upgrade to a powered bed, the general trend has been for the user to sell the manual bed and purchase a powered bed, or to trade in the manual bed and pay extra for the powered bed. This has generally necessitated that adjustable bed dealers carry inventories of both manual and powered beds. Another problem typically encountered with powered beds is that of repair. In very early models, a motor failure required a service call by a repairman and sometimes resulted in temporary loss of bed function until the motor problem was resolved. Improved beds provided an emergency handcrank which could be used to power the bed manually until the motor was repaired. A further improvement is disclosed in U.S. Pat. No. 4,545,084 (Peterson) which describes a modular drive arrangement for adjustable beds. The Peterson invention provides individually interchangeable motor and manual drive units which allegedly may be interchanged without disturbing the patient. Unfortunately, assuming a person is in the bed, it is necessary to crawl under the bed to interchange one of the Peterson drive units. To ensure sufficient clearance for the serviceman to be able to crawl under the bed, it is necessary that the bed have adjustable legs so that the entire bed can be raised off the floor (presumably the patient must be removed from the bed before this can be accomplished). Another problem with the Peterson bed is that the service person must troubleshoot a defective bed to determine which drive unit is in need of repair. To diagnose a defective bed, it is again necessary to crawl under the Peterson bed to determine which drive unit is defective, or else remove the mattress and bedding (and the patient) to enable a visual inspection of the moving parts.
A variety of drive units are known for powered beds. Some beds utilize hydraulic or pneumatic actuators, while others use electric motors. Among those powered by electric motors, some use multiple motors per bed, usually one motor for each drive shaft. An advancement over this scheme is a bed which uses a single motor and appropriate coupling mechanisms to activate particular drive shafts.
One example of a single-motor drive unit for an adjustable bed is disclosed by Houlberg et al. in U.S. Pat. No. 4,324,010. Houlberg et al. use a unidirectional motor which necessitates a more complex clutch assembly comprising eight solenoids and two gears per drive shaft.
U.S. Pat. No. 4,472,846 (Volk, Jr. et al.) discloses a coupling system for an adjustable bed which utilizes a single reversible motor which drives one or more adjusting mechanisms through individual clutches. According to the patent, a salient feature of the invention is the use of a relatively light (i.e., weak) restoring spring to disengage the clutch and corresponding less powerful solenoids to overcome the spring when engaging the clutch. Unfortunately, it is necessary to unload each clutch prior to disengagement to prevent the clutch mating surfaces from locking or binding after the solenoid has been de-energized. This unloading is accomplished by momentarily reversing the direction of the bidirectional motor which jogs the gear train sufficiently to take the forces off of the clutch so that it can release. This requires complex control circuitry as shown in FIGS. 18 and 19.
What is needed, then, is a coupling mechanism for a bi-directional single-motor drive unit which comprises a clutch which will not bind up upon disengagement and does not require reversing the motor to accomplish disengagement.
Finally, adjustable beds are, of course, usually more complicated in construction than conventional beds. Due to this more complex construction, it is generally more difficult to disassemble, transport and reassemble adjustable beds. This is especially troublesome in that there is usually a much greater need to transport adjustable beds than conventional beds.